Glass economic importance

A value of Ai/298 —199.2 8.4 kJ/mol (—47.61 2.0 kcal/mol) has been calculated for this reaction, which is of considerable economic importance to glass manufacturers because 2 3 during glass (qv) processing are gready increased by the presence of water. For this reason anhydrous borates or... 

Most abundant group of materials, composed of silicates of aluminium with sodium, potassium, calcium, and rarely barium. Most economically important mineral. Used for ceramics, glass, abrasive wheels, cements, insulation and fertilizer. 

This method provides unvaluable informations on the short and medium range order in disordered atomic architectures amorphous solids, glasses but also liquids or complexes in solution. The fast development and the economical importance of... 

It has long been known that it is possible to modify the electrical properties of polymers by means of conductive admixtures of many kinds or, rather, to make them conductive. Despite this, electrically conductive polymers are still not of any great economic importance as materials. They do, however, play an indispensable role in many specialized technical applications. They are mostly manufactured by incorporating electrically conductive carbon black or carbon fibers in a variety of polymers, especially thermoplastic polymers. Other conductive additives, such as steel fibers, aluminum flakes, metal-coated carbon fibers, metal-coated hollow glass spheres, and low melting metallic alloys have not so far played any decisive part in the development of electrically conductive polymers. 

Effect of Plasticizers. The phenomenon of plasticization results from the addition of a diluent (called plasticizer) to a polymer in which it is miscible in all proportions so as to lower its glass transition temperature. This diluent introduces free volume in the material and, like any solvent, promotes polymer-diluent interactions at the expense of polymer-polymer interactions. This phenomenon of plasticization results in the decrease of Tg. In the case of poly(vinyl chloride) (PVC), it is a process of great economic importance because most of the PVC annually produced and used is plasticized. 

All these polymers exhibit a glass transition temperature higher than room temperature, and most of them are amorphous. Due to either the size of their substituent or their molecular symmetry, some of them are semicrystalline. They have a definite melting point, and according to its value they exhibit a mechanical behavior more complex than that of amorphous polyvinyls. Depending upon the nature of substituents A and B, the physicochemical properties of polymers of this family can be very different, thus enabling them to be used in many fields. Their overall economic importance is considerable but variable depending upon their stmcture it is not possible to make an exhaustive presentation of them. 

Recycling is particularly important for the building civil engineering market, the sector with the second-largest consumption of thermoplastics. Unfortunately, plastics recycling presents technical and economic difficulties and is less advanced, industrially, than that of metals or glass. 

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

Acrylic fibers (PAC) are, together with PES and PA, the most important synthetic fibers [154], For methods of production and properties of PAC fibers see [96, pp. 629-642], To obtain fibers with satisfactory dyeing properties, anionic comonomers are used. In this way, the glass transition temperature Tg is lowered and anionic groups are available that can act as dye sites for cationic dyes. Thus, acrylic fibers are reliably and economically dyeable wth cationic dyes. 

Vegetable fibres (including wood fibres) represent a good replacement solution for glass and carbon fibres for the reinforcement of composites based on a thermoplastic matrix. The advantages of vegetable fibres are economically and ecologically important ... 

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